Is it ever worth buying an alternative extension to a domain that contains a trademarked name? i.e McDonalds.food or McDonalds.energy Thank you.
Definitely not - you will neither be able to use it to develop a site (because will be sued,) nor sell it as nobody wants trademarked domains.
No, it is not worth buying if there is any possibility of confusion on the part of consumers. mcdonalds.energy might be doable if you have a company named Mcdonald's Energy. But forget the food TLD. McDonald is a surname, McDonald's is the possessive. McDonald's does not have trademark rights to all uses of the word "McDonald".
if you buy trademarks domain it can be suspended so you ill be loose big invest and time so try another names